SINGAPORE: Showers on Wednesday (Sep 25) alleviated hazy conditions in Singapore, improving air quality markedly.
Pollutant Standards Index (PSI) readings have been in the moderate range since Tuesday night, falling to between 62 and 67 at about 4pm.
This is the first time in five days that readings across the island have fallen below 70.
PSI readings of 50 and below denote “good” air quality, 51-100 is “moderate” and 101-200 “unhealthy”.
The one-hour PM2.5 concentration readings at 4pm fell to single digits, ranging between 3-9µg per cubic metre, before rising slightly.
PM2.5 is a measure of tiny particles less than 2.5 micrometres in diameter in the air. When the PM2.5 reading is in the elevated range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions.
According to NEA, one-hour PM2.5 readings are a "good indicator of current air quality", and can be used for those deciding whether to go for immediate outdoor activities, such as a jog.
In a haze update on Wednesday evening, the National Environment Agency (NEA) said that rain is forecast over Singapore in the next few days.
For Thursday, the one-hour PM2.5 readings are expected to be "normal", and the 24-hour PSI is forecast to be in the "good" to "moderate" range.
"Although recent showers have brought some improvement to the haze situation in the region, hotspot activities in Sumatra can be expected to persist," said NEA.
"Singapore may still experience occasional slightly hazy conditions over the next few days if the prevailing winds blow smoke haze from Sumatra toward Singapore."
The fresh bout of rain also brought respite to rain-deprived Singapore, almost a month after the driest and warmest August on record.
The Meteorological Service Singapore (MSS) expects thundery showers in the afternoon from Thursday to Sunday in NEA's four-day weather outlook.
In an advisory on Aug 16, the Met Service said Singapore was experiencing its first dry spell in more than five years.
A dry spell is defined by MSS as a period of at least 15 consecutive days with daily total rainfall of less than 1mm.
The haze situation has also eased in the region, as showers over Sumatra and Kalimantan have caused the number of hotspots in Indonesia to drop by more than 40 per cent, from 3,150 two days ago to 1,744 on Wednesday.